Groovy Cookbook

Groovy programming language tutorials and howtos.

These 10 New Features Make Groovy 4.0 AWESOME!

Sealed types, switch expressions, and record types. Here are just a few new features introduced in the latest Groovy 4.0 release. In this video, I want to show you ten things that make Groovy 4.0 amazing. And to keep this video short, we’re not going to dive deep into each of them. Instead, I intend to give you a quick overview of the new features.

Groovy Trampoline Closure - a step into recursive closures

A few weeks ago an interesting question was asked on the StackOverflow. Someone experimented with a recursion in Groovy and stepped into Closure.trampoline() [1]. It quickly turned out that using TrampolineClosure makes a recursive execution slower. Is this a valid behavior, or do we do something wrong?

Spock random order of tests - how to?

Spock Framework executes test methods (features) in a single class (specification) in the declaration order. There is nothing wrong in this default behavior - we should write tests with their isolation in mind. However, in some cases, we would like to randomize test methods execution. Today we are going to learn how to do it.

Groovy Regular Expressions - The Benchmark (Part 2)

In the second part of the "Groovy Regular Expression" blog post, I want to show you some benchmarks. And let me make one thing clear - the following results you are going to see are not scientific proof. I present those results only to give you a hint about the overall performance of some cool features you have seen before.

Groovy Regular Expressions - The Definitive Guide (Part 1)

Welcome to "Groovy Regular Expressions - The Definitive Guide"! In the next 15 minutes, you are going to learn everything you need to start working productively with regular expressions in Groovy programming language. Let’s get started!

How to remove any class annotation with Groovy compiler configuration script?

One of the most interesting Groovy features is its ability to configure advanced compiler[1] options using DSL script. It becomes handy when you want to apply some global modifications to all Groovy classes. (For instance, you want to add @CompileStatic annotation to all classes, without applying changes to the source code). In most cases, you want to add something to the existing source code, e.g., classes imports or useful annotations, but what if we want to remove one annotation or another?

GraalVM native image inside docker container - does it make sense?

We have learned how to create GraalVM native image from standalone Groovy script in the previous blog post. Today we continue the experiments, and this time we are going to create a Docker image to see what are the benefits and drawbacks of this solution.

GraalVM with Groovy and Grape - creating native image of a standalone script

The Apache Groovy programming language has extraordinary scripting capabilities. When you combine it with the Grape dependency management system, it turns out that the sky is the limit. In one of the previous blog posts, I explained how you can start compiling Groovy code to the native binary files, using GraalVM’s native-image compiler. This time I tried to do the same with the Groovy script that uses Grape to provide an external library to the classpath. I thought it won’t be possible, but luckily - I was wrong.

Spock assertion inside if-statement doesn't work - why?

Spock Framework is one of my favorite tools in the Groovy ecosystem toolbox. It makes writing automated tests a few times more pleasant thanks to its opinionated syntax. From time to time I see some corner cases where Spock behaves unexpectedly. Today I would like to show you one of these corner cases and explains what happens under the hood.

JUnit Assume.assumeNotNull(obj) throws NullPointerException in Groovy - what's wrong?

Ignoring some of the unit tests when given conditions are not satisfied is a handy feature of a JUnit framework. I guess you have used many times constructions like Assume.assumeTrue(expr) or Assume.assumeNotNull(expr) in your test code. Today I would like to show you one pretty interesting corner case when the usage of Assume.assumeNotNull(expr) throws NPE in the unit test written in Groovy.

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